PHP Implementations

HHVM – http://hhvm.com/
HHVM is an open-source virtual machine designed for executing programs written in Hack and PHP. Developed by Facebook.

JPHP – – http://j-php.net/ – https://github.com/jphp-compiler/jphp – @jphpcompiler
JPHP implements PHP on the Java VM. It supports many features of the PHP language (5.6+).
JPHP is a compiler like javac, it compiles PHP source to JVM bytecode and executes the result on the Java VM.
Its basically a pure language implementation, because there are no additional libraries, like cURL or DB abstraction layers like PDO.
Boils down to: you can’t run your favorite Framework or CMS using JPHP, but you can use JPHP to stay in the PHP syntax and start using Java libs and classes and execute your JPHP code on Android.

HippyVM – http://hippyvm.com/
An implementation of the PHP language in RPython (Restricted Python). The PHP code is translated to RPython and then to native C.
The development of this approach was sponsored by Facebook, as part of finding an alternative to the Zend Engine.
They tried to get VC funding, but failed. Lesson learned: development of a HLL-VM is no startup business.

PyHP.js is a PHP interpreter in JavaScript running in a web browser. The underlying PyHP PHP interpreter is written in Python is translated into C using RPython. This is translated into JavaScript using emscripten. The resulting javascript file is asm.js. It can be loaded in any browser or ran with Node.js.

Peachpie – http://www.peachpie.io/ – iolevel – https://twitter.com/pchpcompiler
Peachpie compiles PHP to the .NET environment.
It stands on the shoulders of Phalanger, but uses the new Roslyn Compiler Infrastructure from Microsoft.
It enables you to interface .NET libraries and classes. For example: WordPress running on .NET/Mono – http://www.wpdotnet.com/http://www.wpdotnet.com/